var nums = [
  /*'1',*/ '2', '3', '4', '5', '6', '7', '8', '9', /*'0',*/
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', /*'I',*/ 'J', 'K', 'L', 'M', 'N', /*'O',*/ 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
  'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', /*'i',*/ 'j', 'k', /*'l',*/ 'm', 'n', /*'o',*/ 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
];

export default function drawCode(el, options = {}) {
  var children = el.childNodes;
  if (children && children.length > 0) {
    for (var child of children) {
      el.removeChild(child)
    }
  }

  var canvas = document.createElement('canvas');
  canvas.width = options.width ? options.width : 160;
  canvas.height = options.height ? options.height : 40;
  canvas.style.cursor = 'pointer';
  el.appendChild(canvas);

  var context = canvas.getContext('2d'); //获取画布2D上下文
  var str = '';
  context.fillStyle = '#ffffff'; //画布填充色
  context.fillRect(0, 0, canvas.width, canvas.height); //清空画布
  context.fillStyle = 'black'; //设置字体颜色
  context.font = '25px Arial'; //设置字体
  var rand = new Array();
  var x = new Array();
  var y = new Array();
  for (var i = 0; i < 4; i++) {
    rand.push(rand[i]);
    rand[i] = nums[Math.floor(Math.random() * nums.length)]
    x[i] = i * (options.x ? options.x : 40) + 10;
    y[i] = options.y ? options.y : Math.random() * 20 + 20;
    context.fillText(rand[i], x[i], y[i]);
  }
  str = rand.join('').toUpperCase();
  //画3条随机线
  for (var i = 0; i < 3; i++) {
    drawline(canvas, context, options);
  }
  // 画30个随机点
  for (var i = 0; i < 30; i++) {
    drawDot(canvas, context);
  }
  return str;
}

// 随机线
function drawline(canvas, context, options) {
  context.moveTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)); //随机线的起点x坐标是画布x坐标0位置，y坐标是画布高度的随机数
  context.lineTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)); //随机线的终点x坐标是画布宽度，y坐标是画布高度的随机数
  context.lineWidth = 0.5; //随机线宽
  context.strokeStyle = 'rgba(50, 50, 50, 0.3)'; //随机线描边属性
  context.stroke(); //描边，即起点描到终点
}

// 随机点(所谓画点其实就是画1px像素的线，方法不再赘述)
function drawDot(canvas, context) {
  var px = Math.floor(Math.random() * canvas.width);
  var py = Math.floor(Math.random() * canvas.height);
  context.moveTo(px, py);
  context.lineTo(px + 1, py + 1);
  context.lineWidth = 0.2;
  context.stroke();
}
